2,5 and 2,6 DCBQ

Dear researchers and teachers of photosynthesis,
What are the functionnal differences between 2,5 di-chlorobenzoquinone
and 2,6 di-chlorobenzoquinone, when used as PSII acceptors?
Thank you in advance,
Pascal Meunier
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http://bilbo.bio.purdue.edu/~pmeunier
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